This invention relates to a device which is attached to the boom of a crane, for the precise and remote manipulation of an object such as a cross-arm or insulator, adjacent to energized overhead high voltage transmission lines, or the lines themselves.
The replacement and installation of cross arm members or insulators on overhead transmission towers is generally accomplished, whenever possible, while the electrical transmission lines are energized. It is common to find several rows of transmission towers supporting two or more vertically separate electrical transmission lines located in relatively close proximity. This confined overhead working area emphasizes the need for the precise elevating and manipulation of objects so as to avoid accidental arcing between the energized lines and the object with obvious dire consequences to workmen and machinery. A convenient practise is to employ a helicopter to elevate such objects to workmen on the tower. However, where a tower supports vertically separated energized lines, wind gusts and rotor downwash make this practice difficult and may require the de-energising of a portion of the electrical transmission line. Such de-energizing is undertaken only as a last resort. The present invention provides a relatively easily controllable apparatus, which is able to elevate and accurately position power transmission lines or elongate, electrically conductive structural members such as supporting arms for power lines and insulators within the generally confined overhead work space associated between vertically separated electrical transmission lines or between horizontally spaced transmission towers. Further, the present invention permits elongated electrically conductive structural members, such as supporting cross arms for power lines and insulators, to be elevated generally parallel to and above one or more energized power lines with minimum displacement therefrom, thereby avoiding accidental contact between the lines and the electrically conductive structural members. Once elevated to the required position, for example, a replacement cross arm may be arcuately rotated in a horizontal plane into a preselected position adjacent to the electrical transmission line-supporting tower and generally at right angles to the power lines.